Printhead module for additive manufacturing system

ABSTRACT

A module for an additive manufacturing system includes a frame, a dispenser configured to deliver a layer of particles over a platen, an energy source to generate a beam to fuse the particles, and a metrology system having a first sensor to measure a property of the surface of layer before being fused and a second sensor to measure a property of the layer after being fused. The dispenser, first sensor, energy source and second sensor are positioned on the frame in order along a first axis, and the dispenser, first sensor, energy source and second sensor are fixed to the frame such that the frame, dispenser, first sensor, energy source and second sensor can be mounted and dismounted as a single unit from a movable support.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.15/265,618, filed Sep. 14, 2016, which claims priority to U.S.Provisional Patent Application Ser. No. 62/262,708, filed on Dec. 3,2015, and to U.S. Provisional Patent Application Ser. No. 62/219,605,filed on Sep. 16, 2015, the entire contents of each being incorporatedby reference.

TECHNICAL FIELD

This invention relates to additive manufacturing, and more particularlyto a 3D printing process in which a layer of powder is dispensed, fusedand formed into a 3-dimensional shape.

BACKGROUND

Additive manufacturing (AM), also known as solid freeform fabrication or3D printing, refers to any manufacturing process where three-dimensionalobjects are built up from raw material (generally powders, wires,liquids, suspensions, or molten solids) in a series of two-dimensionallayers or cross-sections. In contrast, traditional machining techniquesinvolve subtractive processes and produce objects that are cut out of astock material such as a block of wood or metal.

A variety of additive processes can be used in additive manufacturing.The various processes differ in the way layers are deposited to createthe finished objects and in the materials that are compatible for use ineach process. Some methods melt or soften material to produce layers,e.g., selective laser melting (SLM) or direct metal laser sintering(DMLS), selective laser sintering (SLS), fused deposition modeling(FDM), while others cure liquid materials using different technologies,e.g. stereolithography (SLA).

Sintering is a process of fusing small grains (or particles), e.g.,powders, to create objects. Sintering usually involves heating a powder.When a powdered material is heated to a sufficient temperature(typically lower than the melting point) in a sintering process, theatoms in the powder particles diffuse across the boundaries of theparticles, fusing the particles together to form a solid piece. Incontrast to melting, the powder used in sintering need not reach aliquid phase. As the sintering temperature does not have to reach themelting point of the material, sintering is often used for materialswith high melting points such as tungsten and molybdenum.

Both sintering and melting can be used in additive manufacturing. Thematerial being used determines which process occurs. An amorphous solid,such as acrylonitrile butadiene styrene (ABS), is actually a supercooledviscous liquid, and does not actually melt; as melting involves a phasetransition from a solid to a liquid state. Thus, selective lasersintering (SLS) is the relevant process for ABS, while selective lasermelting (SLM) is used for crystalline and semi-crystalline materialssuch as nylon and metals, which have a discrete melting/freezingtemperature and undergo melting during the SLM process.

Conventional powder dispensing systems that use a laser beam or electronbeam as the energy source for sintering or melting a powdered materialtypically direct the beam on a selected point in a layer of the powderedmaterial and selectively raster scan the beam to locations across thelayer. Once all the selected locations on the first layer are sinteredor melted, the platform which supports the powder is moved downwards anda new layer of powdered material is deposited on top of the completedlayer. The process is repeated layer by layer until the desired objectis produced.

SUMMARY

In one aspect, a module for an additive manufacturing system includes aframe configured to be removably mounted on a movable support, adispenser configured to deliver a layer of particles on a platen that isseparate from the frame or an underlying layer on the platen, a heatsource configured to heat the layer of particles to a temperature belowa temperature at which the particles fuse, and an energy sourceconfigured to fuse the particles. The dispenser, heat source and energysource are positioned on the frame in order along a first axis, and thedispenser, heat source and energy source are fixed to the frame suchthat the frame, dispenser, heat source and energy source can be mountedand dismounted as a single unit from the support.

In another aspect, a printhead assembly for an additive manufacturingsystem includes a printhead support and a plurality of printhead modulesremovably mounted on the printhead support. Each printhead module issubstantially identical in physical configuration. Each printhead moduleincludes a frame removably mounted on the support and a dispenserconfigured to deliver a layer of feed material on a platen that isseparate from the frame, or an underlying layer on the platen. Thedispenser is fixed to the frame such that the frame and dispenser can bemounted and dismounted as a single unit from the support.

In another aspect, an additive manufacturing system includes a platen tosupport an object to be fabricated, the platen having a top surface, aprinthead assembly movable relative to the platen in a directionparallel to the top surface, an actuator coupled to at least one of theprinthead support and the platen to generate relative motiontherebetween, and an energy source configured to fuse feed material. Theprinthead assembly includes a printhead support, and a plurality ofprinthead modules removably mounted on the printhead support. Eachprinthead module is substantially identical in physical configuration.Each printhead module includes a frame removably mounted on the support,and a dispenser configured to deliver a layer of particles on a platenthat is separate from the frame, or an underlying layer on the platen.The dispenser is fixed to the frame such that the frame and dispensercan be mounted and dismounted as a single unit from the support;

Features of any of the above aspects can include one or more of thefollowing. The dispenser may include a reservoir to hold the particlesand a conduit coupled to the reservoir and extending along a second axisperpendicular to the first axis. The conduit may have a continuous slotor a plurality of apertures through which the particles are dispensed.The dispenser may include a rotatable auger positioned in the conduit toconvey the particles along the second axis. The dispenser may include aplurality of nozzles and the dispenser is configured to eject theparticles in a carrier fluid through the nozzles. The dispenser may beconfigured to dispense particles to a region on a second axisperpendicular to the first axis that extends beyond an edge of thedispenser. The dispenser is configured to dispense particles at least upto an edge of the frame. A roller or blade may extend along the secondaxis and be configured to smooth the layer of particles.

The heat source may include an array of heat lamps. The heat lamps maybe disposed in a hexagonal closest packed array. The heat lamps may bearranged with vertical longitudinal axes, or with longitudinal axes at anon-zero angle relative to vertical. The energy source may be configuredto generate a beam.

The energy source may be slidably mounted to the frame so as to bemovable along a second axis perpendicular to the first axis, and theassembly may include a motor fixed to the frame and configured to movethe energy source along the second axis such that a spot of impingementof the beam on the layer of particles is movable along the second axis.The energy source may be configured to deflect the beam along a secondaxis perpendicular to the first axis. The energy source may be a laseror an ion beam source. The energy source may include a digitalmicromirror device. The digital micromirror device may include a lineararray of mirrors extending along a second axis perpendicular to thefirst axis.

A second dispenser may be fixed to the frame and configured to deliver alayer of second particles on the support or the underlying layer. Thesecond dispenser may be positioned between the dispenser and the heatsource. The second particles may have a different size or a differentcomposition than the particles.

A metrology system may be fixed to the frame. The metrology system mayinclude a sensor disposed before or after the dispenser in the orderalong the first axis. The metrology system may include a first sensordisposed before the dispenser in the order along the first axis and asecond sensor disposed after the energy source in the order along thefirst axis. The metrology system may include a thermal imager or anoptical camera.

Advantages of the foregoing may include, but are not limited to, thefollowing. Components of the additive manufacturing system may beinstalled and removed as a unit, permitting easier construction andrepair. For example, the printhead may be operable as a “plug and play”module. A standardized printhead configuration may enable scaling ofadditive manufacturing systems to accommodate the size of the object tobe fabricated. The throughput, build bed size, resolution and/or qualityof the additive manufacturing process may be improved.

DESCRIPTION OF DRAWINGS

FIG. 1A illustrates a schematic of an exemplary additive manufacturingsystem.

FIG. 1B illustrates a schematic of an exemplary additive manufacturingsystem.

FIG. 2 is a top view of the additive manufacturing system illustrated inFIG. 1A.

FIG. 3 is illustrates a side view of a printhead module.

FIG. 4 illustrates a top view of a printhead module.

FIG. 5 illustrates a perspective view of a feed material dispenser.

FIG. 6 illustrates a heat lamp array.

FIG. 7 illustrates a schematic of an exemplary additive manufacturingsystem.

DETAILED DESCRIPTION

An additive manufacturing system deposits a layer of feed material (forexample, powders, liquids, suspensions, molten solids) on a platen, andthen fuses portions of the layer of feed material. One or more feedmaterial dispensers can deliver one or more feed materials to depositthe layer of feed material, and in some implementations the feedmaterial can be selectively deposited by the one or more feed materialdispensers. After the feed material is dispensed onto the platen, aspreader, for example, a roller or a blade, can spread the feed materialover the platen to a higher uniformity or compaction, if desired. Fusingthe desired portions of the layer of feed material can be achieved bysupplying energy from one or more energy sources. The energy sources canapply energy to a spot, e.g., a single voxel at a time, or across anarea, e.g., over multiple voxels simultaneously. For example, the energysource can include one or more lasers and/or arrays of heat lamps. Thearrays of heat lamps can be located above or below the platen orelsewhere in the chamber of the additive manufacturing apparatus. Energyfrom the energy source heats up the feed material and causes it to fusetogether to form a solid piece. The additive manufacturing system canalso include one or more metrology systems that measure variousparameters of the additive manufacturing process, for example,thermal/temperature uniformity, surface roughness or uniformity, imageof the surface, and/or stress of the deposited feed material.

It is desirable to have a standardized printhead module that includesvarious printhead components, for example, a feed material dispenser, aheat source and an energy source. “Standardized” in this contextindicates each printhead module is substantially identical in physicalconfiguration (there can be software exceptions such as serial number orfirmware version that vary between dispensers). The standardizedprinthead module simplifies construction and repair of additivemanufacturing systems, e.g., the printhead module may be operable as a“plug and play” module that would be operable in any compatible additivemanufacturing system. A standardized configuration of printhead modulescan also enable scaling of additive manufacturing systems to accommodatethe size of the object to be fabricated.

It is desirable to improve the throughput and build bed size of theadditive manufacturing process. This can be achieved by performing theadditive manufacturing process using a plurality of printhead modules.

The printhead modules can be removably mounted on a support to form aprinthead assembly. The printhead assembly can include mechanisms, forexample, actuators, that allow the printhead modules to move relative toone another. In addition, the printhead module can include mechanisms,for example, actuators, that allow the components in the printheadmodule to move relative to one another.

The printhead assembly can also include “global” printing components;for example, feed material dispensers, dispersion mechanisms, metrologysystems and coolant dispensers, in addition to the printhead modules. Inthis context, “global” means that the components are directly mounted tothe printhead support, rather than secured within a printhead, and areconfigured to affect or measure a region of the layer of feed materialdispensed by multiple printheads.

Moreover, the printhead system can be mounted on or attached to amechanism (for example, a robot arm, a cantilever or a gantry) thatallows it to move relative to the platen.

FIG. 1A illustrates a schematic of an exemplary additive manufacturingsystem 100. The system 100 includes and is enclosed by a housing 102.The housing 102 can, for example, allow a vacuum environment to bemaintained in a chamber 101 inside the housing, e.g., pressures at about1 Torr or below. Alternatively the interior of the chamber 101 may bemaintained under a desired gas environment, e.g., a gas that has beenfiltered to remove particulates, or the chamber can be vented toatmosphere. The gas can enter the chamber 101, from a gas source (notshown), through a gas inlet 103. The gas from the chamber can be removedthrough a vent (or outlet) 104.

The system 100 includes a platen 105 that receives or supports the layerof feed material. The platen 105 can include or be placed above a heater109, e.g., a resistive heater or a lower lamp array, which can heat theplaten 105 and thus heat the feed material deposited on the platen 105.

A printhead assembly that carries out the additive manufacturing processis positioned above the platen 105. The printhead assembly includes aprinthead support configured to carry one or more printhead modules.

Each printhead module is removably mounted on the support. “Removablymounted” in this context means that the printhead can be installed suchthat the printhead is mechanically held in a fixed position relative tothe support, but that the printhead module can be removed by use ofstandard hand-held construction tools, e.g., wrenches or powerscrewdrivers, and without damage to the printhead module or theprinthead support. For example, a frame of the printhead module couldhave projections that engage surfaces of the support. For example, aflange projecting horizontally from the printhead module could rest on arim of a portion of the support that surrounds the printhead module.When an operator desires to remove the printhead, the printhead issimply lifted out. Alternatively or in addition, a frame of theprinthead module can be secured by mechanical fasteners, e.g., nuts andbolts, to the support. When an operator desires to remove the printhead,the bolts are loosened and the printhead is lifted out.

In the example of FIG. 1A, the printhead support is provided by aprinthead platform 150 that is configured to carry one or more printheadmodules 210 (see FIG. 2). Each printhead module 210 is removably mountedon the platform 150. The printhead platform 150 can be supported by andform part of a gantry 130. An actuator system 152 allows the printheadplatform 150 to move across the platen 105 (for example, along they-axis). The platform 150 and the platen 105 are separate from oneanother, and neither supports the other. For example, the platform 150is not mounted on the platen 105.

A controller 190 controls various aspects of the additive manufacturingprocess. For example, the controller 190 controls the actuator system152 and therefore the motion of the printhead platform 150. Thecontroller 190 can also control the relative motion and operation ofprinthead modules (not shown) included in the printhead platform 150.The controller can also control the operation of various “global”printing components included in the printhead platform 150.

In FIG. 1B, the printhead platform 150 is attached to a robot arm 131 ofa robot 132 that can move the printhead platform 150 over the platen105. Again, each printhead module 210 (see FIG. 2) is removably mountedon the platform 150. The motion of the robot arm 131 is controlled bythe controller 190.

The printhead platform 150 can be a generally rectangular plate withapertures into which the printhead modules 210 are fit. Although FIGS.1A and 1B both show a platform that is a generally horizontal plate, thesupport can have other forms, e.g., the support can be a frame or avertical plate to which the modules are secured. It should be understoodthat discussion of attachment of the components to the printheadplatform can be applied to attachment of the components to the printheadsupport.

FIG. 2 is a top view of the exemplary additive manufacturing systemillustrated in FIG. 1A. The printhead platform 150 is mounted on therails 130 a and 130 b of the gantry 130. By sliding over the rails 130 aand 130 b of the gantry 130—for example, by an actuator—the printheadplatform 150 can traverse over the platen 105 (along y axis).

The printhead platform 150 includes one or more printhead modules 210.As noted above, each printhead module 210 is removably mounted on theplatform 150.

In addition, the printhead 210 and the components in the printhead,e.g., the dispenser, heat source and energy source, are configured suchthat they can be mounted and dismounted as a single unit from theplatform 150. This permits easier construction and repair of theadditive manufacturing system 100.

As shown in FIG. 2, the printhead modules 210 are arranged in astaggered fashion so as to span the entire width of the platen 105. Thispermits a layer of the object to be fabricated with a single pass of theplatform 150 over the platen 105. The printhead modules 210 perform theadditive manufacturing process on rectangular strips of feed materialdeposited on the platen.

The platform 150 can also support global printing components 220 and222. These global printing components are mounted directly on theplatform 150, rather than on the frame of a printhead module 210.Printing component 220 can be a global dispenser that can dispense andsmooth the deposited feed material. Printing component 220 and/or 222can be a global metrology system that can measure various parametersassociated with the additive manufacturing process. The global metrologysystem can comprise one or more of a sensor, a thermal imager or anoptical camera.

In one implementation, as the system 150 moves from left to right (along+y direction) across the platen 105, a first global metrology system 220forms the leading edge of the system, followed by the printhead modules210 which in turn are followed by a second global metrology system 222at the end. The global metrology system 220 at the leading edge of thesystem 150 can therefore measure various parameters such as thetemperature and/or vertical position of the surface, e.g., the platen orunderlying layer, onto which the layer will be deposited. This data canbe fed to the controller 190 to control operation of the printheadmodules 210. For example, if the feed material dispenser iscontrollable, measurements of the height of the surface can be used bythe controller to determine an amount of material to dispense to improvelayer thickness uniformity. Similarly, the data on the temperature ofthe layer can be used to control the power delivered to the heat sourceand/or energy source so that the portions to be fused are raised to auniform temperature. The global metrology system 222 at the trailingedge of the system 150 can measure the various parameters associatedwith the additive manufacturing process, for example, the temperatureand/or surface roughness of the fused/melted feed material. Again, thisdata can be fed to the controller 190 to control operation of theprinthead modules 210, e.g., in a feedback loop to provide improveduniformity.

In some implementations, the global metrology system 222 can be dividedinto several segments along the x direction such that each segment ofthe metrology system is responsible for taking measurements of feedmaterial fused by one or more printhead modules.

In some implementations, the additive manufacturing process can beone-directional, i.e., the additive manufacturing process only occurswhen the system 150 is moving from left to right or from right to left.In another example, the additive manufacturing process can bebi-directional, i.e., the additive manufacturing process occurs when thesystem 150 is moving both from left to right and from right to left. Theglobal printing components 220 and 222 can either be similar (forbi-directional printing) or different (for unidirectional printing).

FIG. 3 is a schematic illustration of the additive manufacturing processby the printhead module 210. The additive manufacturing system 100includes a printhead module 210 that can move over the platen 105 (forexample, along y direction) and perform the additive manufacturingprocess. The various printhead components of the printhead module arearranged along the direction of the additive manufacturing process (forexample, along +y direction). Additionally, in some implementations theprinthead components can move (for example, by an actuator or a motor)relative to the frame of the printhead module. In what follows, theprinthead components will be described in the order in which theyperform the additive manufacturing process on a given strip of depositedfeed material under the printhead module 210.

The printhead module includes a first dispenser 304 (which is on theleading edge of the printhead module 210) that deposits a first feedmaterial 314. A first spreader or levelling/smoothing arm 340 (forexample, a roller or a blade (or knife-edge)) follows the dispenser 304and disperses/smooths the deposited feed material evenly across theplaten 105.

An optional second dispenser 305 can follow the first dispersionmechanism 340 to deposit a second feed material 312. Feed materials 312and 314 can be of different sizes, shapes and/or can have differentmelting temperatures. For example, the second feed material 312 can besmaller than the first feed material 314, and may therefore fill theinterstitial spaces between the particles of feed material 314. Inanother example, the second feed material 312 can be an alloyingadditive or a binder material that behaves differently than feedmaterial 314 when heated to process temperature. For example, feedmaterials 312 and 314 can have different sintering/melting temperatures.The second feed material dispenser 305 is followed by an optional secondspreader or levelling/smoothing arm 341 (for example, a roller or ablade (or a knife-edge)) that disperses/smoothens the deposited feedmaterials 312 or previously levelled feed material 314.

The feed material can be a powder. For example, the feed material can bea powder of particles composed of metal, such as, for example, steel,aluminum, cobalt, chrome, and titanium, alloy mixtures, ceramics,composites, or green sand.

An optional metrology system 352 can follow the dispersion mechanism341, and can comprise one or more of a profilometer, a thermal imager oran optical camera. It can, for example, measure the surface roughness ofthe deposited feed materials. Knowing the roughness of deposited feedmaterial before fusing/melting the feed materials can help in improvingthe quality of the additive manufacturing process by controlling themanufacturing process.

Next is a heat source 334 to raise the temperature of the deposited feedmaterial. In the embodiment described in FIG. 3 the heat source 334 is aheat lamp array. The heat lamp array 334 can heat the deposited feedmaterial 312 (and 314 if present) to a temperature that is below itssintering or melting temperatures.

After the heat source 334 is an energy source 360 to fuse selectedportions of the layer, e.g., by raising the temperature above itssintering temperature or melting temperature (and then permitting theportion to cool). For example, the energy source 360 can emit a beam375. The beam 375 can, for example, be a laser beam generated by alaser, an ion beam generated by an ion source, or an electron beamgenerated by an electron gun. The beam 375 that can raise thetemperature of one or both of the deposited feed materials to near orabove their respective sintering or melting points.

Moreover, the energy source 360 can be selectively activated in order toselectively fuse desired regions of the deposited feed material. Forexample, the energy source 360 can emit the beam 375 that impingescertain portion of the platen, thereby melting one or both the feedmaterial deposited in that portion. Selective heating of certainportions of the feed material by the energy source 360 can be achievedby moving the energy source 360 relative to the printhead module frame,or by moving the beam 375 over the feed material, or both, inconjunction with selective activation of the energy source 360.

For example, the energy source 360 can move along a direction (e.g., thex-axis) perpendicular to the motion of the printhead module (e.g., they-axis) by a motor or an actuator that is controlled by the controller190 (see FIG. 1A). In another example, the energy source 360 may notmove relative to the printhead module frame. However, the energy source360 may include a mechanism, for example, a mirror mounted on a galvo ora piezoelectric micromirror device, that can deflect the beam 375 alongthe direction perpendicular to the direction of motion of the printheadmodule. The micromirror device may include a linear array of mirrorsthat are arranged along the direction perpendicular to the direction ofmotion of the printhead module. In all the aforementioned cases, theposition of impingement of the beam 375 relative to the feed materialchanges.

Where two feed materials with different melting or sinteringtemperatures are used, the energy source 360 can raise the entireportion of the layer below the printhead module 210 to a temperaturebetween the melting or sintering temperatures of the first feed materialand the second feed material. Thus, only one of the feed materials willbe fused. This eliminates the need for selective fusing by the energysource 360.

An optional second metrology system 350 follows the energy source 360.The second metrology system 350 can, for example, measure the properties(temperature, surface roughness etc.) of the melted feed material. Thiscan be used by the controller to adjust the process parameters toimprove the quality of the additive manufacturing process.

FIG. 4 illustrates a top view of an embodiment of printhead module 210that is placed in the x-y plane above the platen (not shown). Becausethe module is configured to move from left to right over the platen(along +y direction), the right end of the module is the leading edgeand the left end is the trailing edge. The module 210 includes aplurality of printhead components. For example, the printhead componentsinclude, in the order from leading edge to trailing edge, a metrologysystem 352, a first dispenser 304, a first dispersion mechanism 340 (forexample, a roller or a blade), a second dispenser 305, a seconddispersion mechanism 341 (for example, a roller or a blade), a firstenergy source 334 (for example, a heat lamp), a second energy source 360(for example, a laser system) and a metrology system 350.

FIG. 5 is a schematic illustration of the feed material dispenser 304described in FIGS. 3 and 4. The dispenser 304 comprises of a conduit 505(for example, a hollow cylinder) that extends across the width of theplaten (along the x-axis) which is substantially perpendicular to thedirection in which the printhead module moves (along x direction) duringthe additive manufacturing process. The conduit 505 is coupled to ahopper 520 which stores the feed material 314. The conduit 505 enclosesa hollow space 510 and an auger 540. The auger 540 is rotatably mountedto the material dispenser 304, and a motor can rotate the auger 520, forexample, by a drive shaft.

As the auger 540 rotates, it draws in feed material 314 from the hopper520. The conduit 505 can have a plurality of openings 545 arranged alongits length (along x direction) from which the feed material 314 can bedispensed onto the platen. The rate of flow of the feed material 314through the openings 545 can be regulated by an actuator 550 which canbe controlled by a controller 190 (not shown). The rate of flow of feedmaterial 314 can also be controlled by changing the rate of rotation ofthe auger 540. For example, increasing the rate of rotation of the auger540 can increase the rate at which feed material is dispensed andvice-versa. In other examples, the conduit 505 can have a continuousslot along the length of the conduit (along x axis).

The dispenser 304 can be configured to dispense the feed material beyondthe edge of the module 210. For example, the dispenser could include anejector that ejects the feed material in a fluid carrier throughnozzles, and the nozzles could be positioned at an angle relative to theplaten surface such that the feed material is dispensed on a portion ofthe platen that lies beyond the extent of the dispenser in the xdirection. This feature can be useful to deposit the feed material inregions of the platen that are not directly under the dispenser 304.This ensures, for example, that if there is a gap between two adjacentprinthead modules of a printhead platform, feed material will bedeposited on the portion of the platen that lies underneath the gap.Also, this ensures that the feed material can be deposited to a part ofthe platen that is not directly underneath a printhead module, forexample, regions close to the edge of the platen.

Alternatively or in addition, the dispenser 304 can be configured todeliver more feed material to at the edges of the printhead module 210(along the x-direction) than at the center of the printhead module. Forexample, the holes at the two ends of the conduit 505 (along thex-direction) can be larger (or more closely spaced) than the holes atthe center of the conduit 505. A spreader, e.g., a blade or roller, thespreader 340, can then be used to spread the extra feed material intothe gap between two adjacent printhead modules of a printhead platform.

FIG. 6 illustrates a heat a heat lamp array 600 that can be included inthe printhead module as an energy source, for example, energy source 334in FIGS. 3 and 4. The heat lamp array 600 comprises a plurality of heatlamps 634 that are arranged in an array, for example, a hexagonalclosest packed array. Each heat lamp 634 can be connected to a powersource through one or more pins 636.

The energy delivered to each heat lamp 634 can be controlled by acontroller (for example, the controller 190 in FIG. 1). Changing theenergy delivered to each of the heat lamp can change the energy radiatedby the heat lamp. Therefore, the spatial distribution of energygenerated by the heat lamp array can be controlled by the controller. Asa result, the portion of the feed material deposited on the platen thatreceives energy from the heat lamp array 600 can have a temperaturedistribution. In other words, the heat lamp array 600 can providecontrol of the temperature distribution of the aforementioned portion ofthe deposited feed material.

In FIG. 6, the heat lamp array 600 is arranged along the z axis, and istherefore perpendicular to the feed material on the platen (which is inthe x-y plane). However, the heat lamp array 600 can also be arranged atother angles to the platen. For example, the lamps could be angled inthe y-z plane to move the region heated closer to the point at which thefeed material is dispensed. As another example, lamps at the edges ofthe array (along the x-axis) could be angled outwardly (in the x-zplane) to provide heat to any feed material into a gap between twoadjacent printhead modules of a printhead platform.

FIG. 7 illustrates a top view of an example of an exemplary additivemanufacturing system 700. As described in FIG. 2, system 700 includesand is enclosed by a housing 102. The housing 102 can, for example,allow a vacuum environment to be maintained in a chamber 101 inside thehousing. Alternatively the interior of the chamber 101 can be asubstantially pure gas, e.g., a gas that has been filtered to removeparticulates, or the chamber can be vented to atmosphere. The gas canenter the chamber 101, from a gas source (not shown), through a gasinlet 103. The gas from the chamber can be removed through a vacuum vent104.

The printhead platform 750 is mounted on the rails 130 a and 130 b ofthe gantry 130. By sliding over the rails 130 a and 130 b of the gantry130, the printhead platform 750 can traverse over the platen 105 (alongy direction). The platform 750 supports a printhead module 710 that canbe, for example, the printhead modules described in FIG. 2, 3 or 4. Theprinthead module 710 is mounted on a track 730 and can move along thetracks in the x direction by an actuator 720. The actuator, andtherefore the position of the module 710 in the system 750 can becontrolled by the controller 190.

In the additive manufacturing system 700, the printhead platform 750moves along the length of the platen (y axis) incrementally. For eachincremental motion of the printhead platform 750, the printhead module710 moves from one end of the platen to another along its width (alongthe x direction). Coupling of the motion of the printhead platform 750(along y direction) with the motion of the printhead module (along xdirection), allows the additive manufacturing process to be performedover the entire platen.

The processing conditions for additive manufacturing of metals andceramics are significantly different than those for plastics. Forexample, in general, metals and ceramics require significantly higherprocessing temperatures. Thus 3D printing techniques for plastic may notbe applicable to metal or ceramic processing and equipment may not beequivalent. However, some techniques described here could be applicableto polymer powders, e.g. nylon, ABS, polyetheretherketone (PEEK),polyetherketoneketone (PEKK) and polystyrene.

The controller 190 and other computing devices part of systems describedherein can be implemented in digital electronic circuitry, or incomputer software, firmware, or hardware. For example, the controllercan include a processor to execute a computer program as stored in acomputer program product, e.g., in a non-transitory machine readablestorage medium. Such a computer program (also known as a program,software, software application, or code) can be written in any form ofprogramming language, including compiled or interpreted languages, andit can be deployed in any form, including as a standalone program or asa module, component, subroutine, or other unit suitable for use in acomputing environment.

The controller 190 and other computing devices part of systems describedcan include non-transitory computer readable medium to store a dataobject, e.g., a computer aided design (CAD)-compatible file thatidentifies the pattern in which the feed material should be depositedfor each layer. For example, the data object could be a STL-formattedfile, a 3D Manufacturing Format (3MF) file, or an Additive ManufacturingFile Format (AMF) file. For example, the controller could receive thedata object from a remote computer. A processor in the controller 190,e.g., as controlled by firmware or software, can interpret the dataobject received from the computer to generate the set of signalsnecessary to control the components of the apparatus 100 to fuse thespecified pattern for each layer.

A number of implementations have been described. Nevertheless, it willbe understood that various modifications may be made. For example,

-   -   The module need not include the heater. The heater can be a        global component, or be mounted on walls of the chamber.    -   The module need not include the energy source. The energy source        can be a global component, or be mounted on walls of the        chamber.    -   Rather than the printhead support moving, the printhead support        can remain stationary while the platen moves laterally to        provide the relative motion between the printhead assembly and        the platen.

Accordingly, other implementations are within the scope of the claims.

What is claimed is:
 1. A module for an additive manufacturing system,comprising: a frame configured to be removably mounted on a support thatis movable along a first axis; a dispenser configured to deliver a layerof particles on a platen that is separate from the frame, or anunderlying layer on the platen; an energy source comprising a lightsource or electron gun configured to generate a beam to fuse theparticles; and a metrology system having a first sensor to measure aproperty of a surface of the layer before being fused and a secondsensor to measure a property of the layer after being fused; wherein thedispenser, first sensor, energy source and second sensor are positionedon the frame in order along the first axis, and wherein the dispenser,first sensor, energy source and second sensor are fixed to the framesuch that the frame, dispenser, first sensor, energy source and secondsensor can be mounted and dismounted as a single unit from the support.2. The module of claim 1, wherein the first sensor is configured tomeasure a surface roughness or temperature of the layer.
 3. The moduleof claim 1, wherein the second sensor is configured to measure a surfaceroughness or temperature of the layer.
 4. The module of claim 1, whereinthe first sensor is configured to measure a surface roughness of thelayer and the second sensor is configured to measure a temperature ofthe layer.
 5. The module of claim 1, further comprising a roller orblade extending along a second axis perpendicular to the first axis andconfigured to smooth the layer of particles.
 6. The module of claim 5,wherein the blade is positioned between the dispenser and the firstsensor.
 7. The module of claim 5, wherein the blade is fixed to theframe such that the frame, dispenser, blade, first sensor, energy sourceand second sensor can be mounted and dismounted as a single unit fromthe support.
 8. The module of claim 1, further comprising a heat sourceconfigured to heat the layer of particles to a temperature below atemperature at which the particles fuse.
 9. The module of claim 8,wherein the heat source is positioned between the first sensor and thelight source.
 10. The module of claim 8, wherein the heat source isfixed to the frame such that the frame, dispenser, first sensor, heatsource, energy source and second sensor can be mounted and dismounted asa single unit from the support.
 11. The module of claim 8, wherein theheat source comprises an array of heat lamps.
 12. The module of claim11, wherein the heat lamps are disposed in a hexagonal closest packedarray.
 13. The module of claim 11, wherein the heat lamps are arrangedwith longitudinal axes at a non-zero angle relative to vertical.
 14. Themodule of claim 1, wherein the energy source is configured to move aspot of impingement of the beam on the layer of particles along a secondaxis perpendicular to the first axis.
 15. The module of claim 14,wherein the energy source is slidably mounted to the frame so as to bemovable along the second axis by a motor.
 16. The module of claim 15,wherein the energy source is configured to deflect the beam along thesecond axis perpendicular to the first axis.
 17. An additivemanufacturing system, comprising: a platen to support an object beingfabricated; a dispenser configured to deliver a succession of layers ofparticles over the platen, the dispenser movable along a first axis andincluding a slot or plurality of openings extending along a second axisperpendicular to the first axis, and wherein the dispenser is configuredto dispense particles to a region on the second axis that extends beyondan edge of the dispenser; and an energy source comprising a light sourceor electron gun configured to generate a beam to fuse particles in anuppermost layer of the succession of layers.
 18. The system of claim 17,comprising a frame and a motor to move the frame along the first axis,and wherein the dispenser is mounted to the frame and the dispenser isconfigured to dispense particles at least up to an edge of the frame.19. The system of claim 17, wherein the dispenser comprises a reservoirto hold the particles and a conduit coupled to the reservoir andextending along the second axis, the slot or plurality of openingsextending from the conduit.
 20. The system of claim 17, wherein thedispenser comprises a plurality of nozzles and the dispenser isconfigured to eject the particles in a carrier fluid through thenozzles.